Answers

In the beginning of the Internet, the transactions were sequentials. That means that everything were run one after the other. But with new technology like PUSH, you can have lot's interactions run in parallel like polling for example.

The goal of a fork logical action is to run request in parallel of the main script. You could have polling requests run in a fork in parallel (ie concurrently) of the main script.

Except you know that such mechanism exists on your application, it should not be necessary to use a fork action in your script.

You should check the NeoLoad documentation to get more details of that fork action.

Not at all. Init and End container are executed once for each virtual user instance. Then the users will execute multiple iterations of the Actions container. So using a fork in Actions won't have any effect.

Why are you trying to use a fork? There's no need to use a fork action in a script for most of the Web applications.